Royal Society, 49 



12**00 as the acceleration of the seconds' pendulum in passing 

 from Paris tQ London. The same acceleration deduced from 

 a comparison of M. Biot's and Capt. Kater's direct measure- 

 ments of the seconds' pendulum, in Paris and in London, 

 comes out 1 1 s, 76 ; or conversely, the length of the seconds' pen- 

 dulum observed by the former in London transferred to Paris, 

 by an assumed retardation of 12 s , gives a length differing from 

 M. Biot's by in '00023. Borda's agrees within in '00079 with 

 M. Biot's ; and Capt. Kater's, so transferred, holds very nearly 

 a mean between the two, but approaches rather nearer to 

 Biot's than to Borda's. 



Nov. 22. — W. A. Mackinnon, Esq. was admitted a Fellow 

 of the Society. 



A paper was read, entitled, " On a peculiarity in the struc- 

 ture of the ductus communis choledochus and of the pancreatic 

 duct in man; by John Davy, M.D. F.R.S." 



The peculiarity noticed by the author, consists of a valvular 

 apparatus formed by delicate angular processes of the mucous 

 coat of the lower part of the ductus communis choledochus and 

 of the pancreatic duct; which he detected by slitting open 

 these tubes under water, and washing off the adhering mucus. 

 The effect of this structure is to prevent any retrograde mo- 

 tion in the fluids conducted by these tubes : and although a 

 very delicate probe may be made to descend through the ducts 

 with facility, its passage in the opposite direction is arrested 

 by the sacculi which are formed by the processes of the inner 

 membrane. This structure is not met with either in the sheep 

 or in the ox, in which animals there is no junction of the bi- 

 liary and pancreatic ducts. 



Another paper by Dr. Davy was read, entitled, H Observa- 

 tions on the action of the mineral acids on copper, under dif- 

 ferent circumstances." 



In prosecuting the researches into the slow operation of 

 electro-chemical agency on the alloys of copper, which was 

 the subject of his former paper published in the Philosophical 

 Transactions, the author was induced to examine the action 

 of the mineral acids on copper, under different circumstances. 

 When atmospheric air was excluded, dilute sulphuric acid, 

 into which a bar of polished copper was immersed, had dis- 

 solved at the end of three months only a very minute quan- 

 tity of that metal, and the bar was slightly tarnished with the 

 black oxide of copper. A similar result was obtained with 

 dilute muriatic acid ; but dilute nitric acid dissolved a larger 

 portion of the metal, and the bar was encrusted with black 

 oxide. When the vessels in which similar experiments were 

 made, were covered only with glass, so as to retard evapora- 



New Series. Vol. 3. No. 13. Jan. 1828. H tion 



